A stool test is the collection and analysis of stool for diagnostic purposes. Some of the most common are: * The stool guaiac test, a common diagnostic screening for colon cancer. * Tests for parasites, which usually enter the digestive tract as part of their life cycle * A test for pH, which can indicate lactose intolerance or infection. * A fecal fat test, which can show malabsorption of fat typical of steatorrhea